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How to Grow Phormium Plants

Guide to Growing New Zealand flax, Flax lily, and Mountain flax

Phormium are a tall genus of hardy perennials.

They range in height from 90 cm to over 3 metres.

Most Phormium grown in gardens are half hardy perennials and bloom in the summer.

They are mainly grown for their attractive leaves that are sword shaped and striped red, white or yellow.

Some common names for members of Phormium include Mountain Flax, Flax Lily and New Zealand Flax.

Phormium tenax
Phormium tenax by Wallygrom.

Phormium Growing and Care Guide

  • Common Names: New Zealand flax, Flax lily, Mountain flax.
  • Life Cycle: Half hardy perennial.
  • Height: Up to 16 feet (5 m).
  • Native: New Zealand, Norfolk Island.
  • Growing Region: Zones 8 to 10.
  • Flowers: Summer.
  • Flower Details: Bright red. Curving. Tubular. Stalks to 16 feet (5
  • Foliage: Sword-shaped. Tough. Up to 10 feet (3 m) long. Green, but ornamental varieties may be pink or bronze. Can have striped edges and ribs of red, white, or yellow.
  • Sowing: Seeds of cultivars may not be true to type (usually revert to green or red). Cover seed. Can be sown in late winter but better results if sown in late autumn. Sow in plug trays under glass to increase germination rate in the spring. Germination time: one to six months. Temperature: ~63°F (17°C). Supply weak potassium permanganate solution to prevent emerging seedlings from dying back. Spacing depends on cultivars. Dwarfs can be spaced at about 12 inches (30 cm) while larger species are best spaced at about 40 inches (1 m).
  • Requirements and care: Full sunlight or partial shade. Sandy, fertile, moist soil. Regular watering during dry periods. Divide after three or four years to maintain vigor. Propagate: by dividing in the spring.
  • Family:
  • Closely Related Species:
  • Miscellaneous:The leaves have been traditionally used in New Zealand to produce fiber. Fairly deer resistant. Although the flowers are not ornamental they produce a lot of nectar and attract lots of birds and pollinating insects to the garden.

How to Grow New Zealand Flax and Mountain Flax

The seeds of New Zealand flax, Mountain Flax and other Phormium species should be sown outdoors in February; just cover the seeds once sown. Alternatively they can be started off indoors; start growing them about 2 to 3 months in advance. The germination time of Phormium seeds varies widely and ranged from one to six months. They should germinate fine at about 15 to 18 degrees centigrade.

Phormium should be spaced 30 cm (small species), 50 cm (medium sized species) or 90+ cm apart (larger varieties). They are quite versatile and can be grown in both sunny and partially shaded areas. The soil that Mountain Flax and other Phormium grows in should be moist, sandy and have a fertile composition.

Caring for Mountain Flax and other Phormium Plants

It is easy to look after Mountain flax they require a moist soil so water regularly, and divide every three years or so to maintain vigorous growth. If you require more Phormium then propagate by division in the springtime.